1. Field of the Invention
The invention relates to an improved additives for drilling fluid during drilling operations. In particular, the additive is formed such that the additive can be incorporated into the drilling fluid with much greater speed, reduction of dust and reduction of volume compared to powdered or ground additives of similar components.
2. Description of the Prior Art
Various drilling fluid additives are known in the art. They are used as lost circulation additives, fluid loss additives, seepage loss additives, viscosifiers, thinners, shale control agents, weighting agents, lubricants, cleaning agents, flocculants, dispersants, anti-foaming agents, buffering or pH control agents and other uses. Some additives perform more than one of these functions or other functions useful in drilling activities. While the types of additives used for this purpose range from organic products to mineral products to polymers, most of these additives are introduced into the drilling fluid as a powder. There are numerous disadvantages to the use of a powder. The primary disadvantage is that the additive is very light causing it to mix slowly with the highly viscous drilling fluid. In drilling operations, speedy incorporation of the additives into the mud and circulation down through the hole is essential and affects the profitability and occasionally the safety of the operation. To overcome this disadvantage of slow incorporation, hoppers have been designed with cyclones, venturis and jets to enhance mixing and to attempt to pull the additives from the hopper into the fluid at a higher rate. In spite of the improvement in technology, mixing is still relatively slow. The flow through the cyclones is slow, clogging occurs, and dust becomes a problem. In certain areas of the world where a zero emission standard is in place, dust is a particular problem. Regardless of the level of emission standards, dust creates a hazard for the workers.
Another problem of traditional powdered additives arises due to the general change in drilling operations. There is a trend toward drilling in deeper water with bigger rigs thus requiring larger volumes of mud and increased weights of mud. Thus, the muds being used tend to be more expensive muds and synthetic oils utilizing greater quantities of weighting material. These factors create a need for larger volumes of additives for various purposes. However, storage space, particularly on an offshore rig, is a limiting factor. In the search for a better additive, huge numbers of organic substances have been tested for their efficiency as lost circulation and seepage control agents. In U.S. Pat. No. 4,217,965 issued to Jim G. Cremeans, it is disclosed that discarded cattle feed can be used as an additive. This organic material is made from cottonseed hulls in combination with cottonseed meal, bentonite, some cottonseed lint and a surface active agent. To make feed for the cattle, these components are heated and then compressed and extruded as pellets. Cremeans discloses that the advantage of using discarded cattle feed is that it avoids the steps of grinding, shredding, and pretreatment processes required when using other organic waste products. The surface active ingredient in the pellet acts as a wetting agent to improve mixing time without further chemical additions. The cattle pellets are relatively dense and thus require less storage space. A major disadvantage of the cattle feed is the inclusion of high protein and carbohydrate content in the cotton meal, which degrades quickly and creates an operating or environmental hazard. A shortcoming of the cattle feed is that it does not immediately break down upon contact with the mud but instead maintains its shape and structure as it is added to the mud. They only begin to breakdown when they are well down the drilling hole.
There is a need to provide additives in a form that minimizes space required for storage and/or shipping. There is a need to provide additives in a form which mixes with the drilling fluid at substantially faster speeds. There is a need for a low or no-dust alternative for delivery of the additives to the drilling fluid. It is an object and a goal of this invention to meet these and other needs. It is an object and a goal of this invention to provide an additive that is quickly and efficiently distributed throughout the drilling fluid upon introduction. These and other objects of the invention will appear to one skilled in the art as the description thereof proceeds.
The present invention discloses a method for creating a dense drilling fluid additive for use in drilling fluids as well as the composition therefor. A method of creating a dense drilling fluid additive from a base material for use in drilling operations includes grinding of the base material or acquiring the base material in a ground form. The ground base material is heated and pressure is applied. This cause the material to compact into a dense form which is forced through apertures creating a pelletized dense drilling fluid additive.
While many lost circulation and seepage control materials are appropriate, a preferred embodiment includes organic material as the lost circulation and seepage control material. This pelletized dense additive for use in drilling operations made from a ground lost circulation and seepage control material that is compressed into a pellet has a density substantially greater than that of the ground lost circulation and seepage control material before being compressed.
While many additives are appropriate, a preferred embodiment includes the use of one or more of the following base materials: lignites, leonardites, lignin-based powders, bitumens, lignosulfonates, asphalts, clays, polyacrylate homopolymers and copolymers, cellulosic polymers, xanthan gums, metal silicates, starches, guar gum, cellulosic fibers, fatty acids, amphoterics, carboxymethyl cellulose, welan gum, hydrocarbon resins, barite, hematite, hydroxyethylcellulose, chlorides, bromides, polyphosphates, zinc, gilsonite, graphite, and coke. These and other base materials are known for use in drilling fluid operations as viscosifiers, thinners, weighting agents, lubricating agents, shale control agents, anti-foaming agents, buffering agents, flocculants, dispersants and the like. The dense drilling fluid additive compressed into a pellet has a density substantially greater than that of the base material in its powder form before being compressed.
Of the organic lost circulation and seepage control materials available to produce the dense drilling fluid additive, a preferred embodiment includes a cellulosic material. In particular, one or more of the following in combination are preferred: ground wood, pine bark, fruit pomace, vegetable pomace, yellow pine, pine bark, corn cobs, peanut hulls, pecan piths, almond shell, corn cob outers, bees wings, cotton burrs, oat hulls, rice hulls, seed shells, sunflower, flax, linseed, cocoa bean, feathers, peat moss, jute, flax, mohair, wool, paper, sugar cane, bagasse, sawdust, bamboo, cork, popcorn, tapioca, and grain sorghum.
The pelletized dense additive, while characterized by increased density, is preferably in the range of xe2x85x9 inch to xc2xe inch for diameter and a range of xe2x85x9 inch to 1 inch for length. The density of the additive ranges widely according to the base material, with the preferred density being the highest ratio of compression achievable based on the characteristics of the material. Many organic materials can be compressed to between two and three times the density of the ground material.
This invention also encompasses a method of performing drilling operations wherein a drilling fluid is circulated in a well being drilled in the ground including grinding a base material to produce granules, heating the granules, pressing the heated granules through apertures such that pellets are formed that are of substantially greater density than the base material, and adding the pellets to the drilling fluid for circulation in the well. The heating is typically a result of the friction produced during the pressing process however, the heat produced in grinding is determined by the characteristics of the particular materials. If sufficient heat is not produced during the grinding process, heat input is added. In the situation where naturally occurring binding agents are not present in the base material, the preferred embodiment includes minimizing the amount of heat produced by the process and adding a binding agent to maintain the dense drilling fluid additive in a pellet form. Examples of preferred binding agents include clays, guar gum, lignosulfonate or wood sugar, starch and the like.
Frequently, base materials are already in a ground form. The method of creating a dense additive from such a base material includes obtaining the ground material and compressing the ground material into a pellet such that the pellet has substantially greater density than the ground fiber before being compressed.
The structure and method of the present invention as well as other features, advantages, benefits and objects thereof over other structures and methods known in the art can be better understood with reference to the detailed description which follows.